It has long been an object of workers in the photographic field to provide a light sensitive material that would provide a colored image of a subject with the colors of the image corresponding to the colors of the subject. Because of the nature of the photographic process and the fact that in most instances a negative image is first formed and then a positive image, a negative color image will not have the same colors and the same areas as the subject but there will be corresponding colors in the same areas. Thus, a negative color image of a red flower with green folliage against a blue sky will show a cyan flower with magenta folliage against a yellow sky. A negative may thus be said to have corresponding colors, though not identical colors.
In the early days of color photography color photographs were made by exposing three separate negatives through three separate filters to provide three separate negatives for the three separate color images. These black and white negatives were then printed to form three separate positives and the separate color value positives were then separately toned, placed in register and the color reproduction of the original subject was produced.
Later, the process was modified to use a multi-color filter in front of a single sheet of negative material, the multi-colored filter being provided by a layer of dyed starch grains or a geometric arrangement of dyed gelatin pieces. These processes require that the silver image either be held immovable with respect to the filter, as with the randomly arranged dyed starch grains, or that the image be aligned with the proper corresponding geometrical pattern of the gelatin filter.
More recently, color photography has relied upon color films that incorporate a plurality of emulsions on a single base with the emulsions being separately sensitized to different wave lengths of light and being treated in the processing so that the emulsions develop colors corresponding to the image of the subject matter. In these processes, all the emulsions are generally simultaneously subjected to the same treatment and the different colors are developed by reason of the differences within the separate emulsions.
Many attempts have been made to produce a single emulsion color film in which the three different colors are produced within a single emulsion layer. Because of the different chemistry necessary to produce the different colors, this has been a difficult problem and has not previously been done on a commercial scale. The advantages of a single emulsion as opposed to a triple emulsion with intermediate separation layers include the advantages of a thinner film and its attendant advantages of superior resolution and greater definition. Furthermore, with the thinner emulsion or series of emulsions, the photographic processing can proceed more readily without the various treatment chemicals being required to penetrate through so much material to react with all of the photochemicals.